The Calpe Conference 2024: A personal view Part Two

By Dr Alex Menez

Part two of the three-part series in which Dr Alex Menez looks into the Calpe Conference which took place earlier this year and shares his view of the discussions.

The second day of the Calpe Conference began with a talk by Dr Jaime Ramos from the University of Coimbra, Portugal.

He discussed the “dramatic changes that occurred after the colonization of the archipelago by humans and the spread of exotic invasive species.”

He noted that there were “huge seabird colonies in the 15th century.”

Great numbers of seabirds would be killed for oil, food, and feathers; “killings of 10,000 Manx Shearwater a night… 700-7,600 Bulwer’s petrel… killings of a thousand Madeiran storm petrels a night.”

He noted the population estimates data from 1996: “Manx Shearwater, perhaps a few individuals… Bulwer’s petrel… 50 pairs… Madeiran storm petrel… around 1000 pairs.”
Jaime held that “correct habitat restoration is possible with strong and persistent efforts,” and that “restoration of seabed colonies should take into account the strong intra- and inter- specific competition for nest sites and invasive mammal predators.”

The next speaker, Professor Juan Carlos Illera from the University of Oviedo, noted that “oceanic islands are excellent systems to test ecological and evolutionary hypotheses,” and explained that over the last three decades Macaronesia has proved to be “an ideal system for evolutionary biologists” to understand how biodiversity “arises and disappears.”
His work with extinct and extant species provides an understanding of “phenotypic evolution processes.”
Throughout the conference, there would be mention of the negative impact of humans in Macaronesia.

Juan shared some of his data regarding this, and reported that “two-thirds of endemic, and around thirteen percent of native avifauna, has gone extinct,” adding that “radiocarbon dating of bone collagen of selected extinct species has provided evidence of a negative causal effect of human colonization.”
Professor Clive Finlayson and Dr Stewart Finlayson, both from the Gibraltar National Museum, University of Gibraltar, and Liverpool John Moores University were the next speakers. Clive explained that a great number of bird species arrive at Atlantic islands each year.

Regarding the arrival of these birds, he said that “my argument is that it’s not so much about getting there, it’s about what you do when you get there.”
Contrary to current views that colonizers are “migratory trans-Saharan birds blown offshore during the course of their migration,” he held that the “Macaronesian terrestrial avifauna is largely derived from the Palaearctic,” and, he noted, “mainly composed of species with broad bioclimatic tolerances and wide latitudinal breeding ranges.”
He concluded that the Macaronesian terrestrial avifauna mostly derives from pre-Saharan migrants/residents, and that Macaronesian woodland avifauna is largely derived from “West European/Biscay breeding birds and West European, western Iberian and Moroccan wintering birds.”

The Macaronesian non-woodland avifauna, he noted, is largely derived from “West European/Biscay breeding birds and West European and western Iberian wintering birds (Azores and Madeira), and from Moroccan breeding and wintering birds (Canaries).”
Contemplating bird arrivals at the Atlantic islands, he finished saying that “ultimately, success has been about hanging on once you got there.”
Following lunch, the next presentation was by Professor Nuno Ferrand from the University of Porto, Portugal.
He explained that the European rabbit originated in the Iberian Peninsula several million years ago, and noted that climatic oscillations during the Pleistocene resulted in “the isolation and genetic differentiation of the European rabbits in two refugia” in Iberia.

The refugia, one in the south-west and the other in the north-east, led “to the emergence” of two subspecies.
He held that “rabbit domestication likely happened in France” and that there was “natural and human expansion of the rabbits from Iberia to North Africa, into the whole of Europe, then the UK, then Australian, and then more than 1000 islands all over the globe.”
Genetic and genomic data were essential to understand on-going speciation in Iberia, and the origins of domestication in Europe, and “the remarkable process of colonization of the Atlantic islands.”

Next on was Dr Africa Gomez from Hull University.
I am sure that all ecologists are interested in refugia and the implications on species, speciation, evolution, and more.
Almost two decades ago, Africa contributed to the development of the concept of persistent founder events in passively dispersed invertebrates and the concept of refugia within refugia.
She noted that the refugia within refugia model has been robustly supported in a range of organisms.

“The Iberian Peninsula held multiple separate refugia during the Pleistocene,” she noted, adding that “Early Pleistocene subdivisions suggest maintenance of these refugia throughout Ice Ages for many taxa.”
She explained that genomic sequencing and analysis is applied to phylogeographic studies, and that ancient DNA and palaeogenetics have “allowed us to sample the genomes of ancient organisms, including those of extinct species.”

The Iberian Peninsula is geographically and climatically complex and, she noted, it “holds about 50% of European plant and terrestrial vertebrate species and more than 30% of European endemic species… multiple refugia in the Iberian Peninsula are reservoirs of biodiversity and genetic diversity that could serve as buffers against extinctions due to future climate changes.”
There is always more to be learnt, and more research to be done, and she ended by noting that “a better knowledge of the refugia in the Iberian Peninsula can aid conservation and mitigation against impacts of future climate change.”

The final talk of the day was by Dr Stewart Finlayson and Professor Clive Finlayson, both from the Gibraltar National Museum, University of Gibraltar, and Liverpool John Moores University.
Stewart explained an interesting outcome of research from excavation material.

He noted that “until recently, it was thought that the azure-winged magpies that breed in the Iberian Peninsula were escapees of pet birds brought back from the far east by Portuguese mariners in the late Middle Ages.”

The entire picture changed, he noted, adding that “going back a few years now, the late 1990s, the remains of this species were found in Gorham’s and Vanguard caves…they were found in Late Pleistocene context… this dated to at least 50 thousand years ago.”

The Gibraltar Pleistocene avifauna “is the richest in species anywhere,” and Stewart described some of the material, noting that “the oldest deposits age to almost 130,000 years ago, the more recent ones are from the Medieval Period, so 900 years ago,” adding that “151 species are found in these caves” that is “30 percent of Europe’s birds.”

Dr Alex Menez is the Senior Scientific and Conservation Officer at the Gibraltar National Museum and has published several papers on natural history in Gibraltar.